The present invention relates to a jack mechanism and, more particularly, to a jack mechanism having two parallel rods that provide positive stops, in each direction, for the rotation of the jack handle so as to prevent overrun of the jack mechanism.
Jack mechanisms are well known and provide a means for exerting a pressure for the lifting of a relatively heavy object for a relatively short distance. The jack mechanism almost always has a lever arm or crank handle attached thereto that provides the operator with a mechanical advantage for turning the shaft of the jack mechanism that is interlinked to the object being lifted. Commonly, the lever arm or crank handle is attached to the mechanism by a pin or key inserted into a complementary keyway of the jack mechanism. The crank handle allows for circular motion to be imparted to the shaft lifting the object so that reciprocating motion, e.g., up-down, or inward-outward movement, is achieved. The operator of the jack mechanism sometimes, due to his/her desire to have the heavy object moved, may inadvertently exert a sufficient force on the crank handle, after the shaft of the jack mechanism has reached an extreme of its movement, to cause a twisting motion to be supplied at a sufficient magnitude to cause the pin of the crank handle to be rung off of the keyway. It is desired that means be provided to prevent the inadvertent severance of the crank handle when the shaft of the jack mechanism has reached either of its extremes of reciprocating movement.